Super absorbent polymer (SAP) is a synthetic polymer material capable of absorbing moisture from about 500 to about 1,000 times its own weight, and each manufacturer has denominated it as different names such as SAM (Super Absorbency Material), AGM (Absorbent Gel Material) or the like.
The super absorbent polymers started to be practically applied in sanitary products, and now they are widely used for preparation of various products, for example, hygiene products such as diapers for children, water retaining soil products for gardening, water stop materials for the civil engineering, sheets for raising seedling, fresh-keeping agents for food distribution fields, or the like.
In recent years, as the application field increases, the super absorbent polymer requires a variety of physical properties such as an absorbency under pressure (AUP), a permeability, an absorption rate or the like, in addition to the basic absorption characteristics (for example, absorption capacity of a target solution such as water).
However, these absorption characteristics required for the super absorbent polymer have a trade-off relation, and there is a limit in improving these characteristics at the same time. This trade-off relation also applies to changes in physical properties depending on the structure of the super absorbent polymer.
For example, as the structure of the super absorbent polymer is improved in density, the absorbency under pressure can be improved, but the absorption rate decreases due to a decrease in the surface area. Conversely, as the surface area of the super absorbent polymer increases, the absorption rate increases, but the absorption characteristics decreases as a whole.
Accordingly, there is an urgent need for a technique capable of improving the overall absorption properties without sacrificing any of the physical properties required for the super absorbent polymer.